The UEFA Champions League is a seasonal football competition established in 1955.[1] The UEFA Champions League is open to the league champions of all UEFA (Union of European Football Associations) member associations (except Liechtenstein, which has no league competition), as well as to the clubs finishing from second to fourth position in the strongest leagues.[2] Prior to the 1992–93 season, the tournament was named the European Cup.[1] Originally, only the champions of their respective national league and the defending champion of the competition were allowed to participate. However, this was changed in 1997 to allow the runners-up of the stronger leagues to compete as well.[3] In the Champions League era, the defending champion of the competition did not automatically qualify until the rules were changed in 2005 to allow title holders Liverpool to enter the competition.[4]

A total of 22 clubs have won the Champions League/European Cup. Real Madrid hold the record for the most victories, having won the competition 13 times, including the inaugural competition. They have also won the competition the most times in a row, winning it five times from 1956 to 1960. Juventus have been runners-up the most times, losing seven finals. Atlético Madrid is the only team to reach three finals without having won the trophy while Reims and Valencia have finished as runners-up twice without winning. Spain has provided the most champions, with 18 wins from two clubs.[9] Italy have produced 12 winners from three clubs and England have produced 12 winners from five clubs. English teams were banned from the competition for five years following the Heysel disaster in 1985.[10] The current champions are Real Madrid, who beat Liverpool in the 2018 final.

Ten different nations have won the Champions League, and thirteen nations have sent a team to the finals. Since the 1996–97 season, however (other than Porto's win in 2003–04) the winners have come from one of only four nations — Spain (11), England (4), Italy (3), and Germany (3) — and (other than Monaco's performance in 2003–04) the runners up have all come from the same four nations.